ROME: Ten dollars a gallon may seem unthinkable to American drivers still smarting from the spike in gas prices to around $4 a gallon. But that was nearly the price that Marco Annarumi faced recently when filling his Jeep on his way home from work.

"It hasn't changed my driving at all -- not a bit -- I just have to work harder," he said with seeming indifference.

High oil prices and high taxes on gas pushed the average price of gasoline to new heights in much of Europe this summer. Yet transportation experts in this laboratory of sky-high fuel prices say that many Europeans, out of necessity, habit or love, have proved surprisingly willing to bear the extra cost of driving. That raises questions as to how effective high prices by themselves can be in achieving the ambitious targets for reducing carbon dioxide emissions that European leaders have committed themselves to meeting.

Gas prices have persuaded some people to drive less. Traffic on the Eurostar train that links London and Paris was up 21 percent in the first three months of 2008. Gas purchases in Italy dropped 10 percent compared with the year before. Sales of gas-guzzling sport utility vehicles have plunged across the continent, just as they have in the United States.